Eyewear projector brightness control

ABSTRACT

Eyewear including a projector having a variable feedback loop controlling a forward current delivered to a colored light source. The colored light source is configured to generate a colored light beam to generate a displayed image. The variable feedback loop in one example has a variable resistance to selectively generate a high brightness image when the eyewear is operated outside, or in a high ambient light setting, and to selectively generate a nominal brightness image when the eyewear is operated inside. A controller selectively controls the drive current delivered to the colored light source to control the brightness mode of the image.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No. 17/697,005 filed on Mar. 17, 2022, and claims priority to U.S. Provisional Application Ser. No. 63/168,377 filed on Mar. 31, 2021, the contents of which are incorporated fully herein by reference.

TECHNICAL FIELD

The present subject matter relates to the field of eyewear.

BACKGROUND

Augmented reality (AR) and virtual reality (VR) eyewear have projectors generating an image that is viewable to a user.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations, by way of example only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements.

FIG. 1A is a side view of an example hardware configuration of an eyewear device, which shows a right optical assembly with an image display, and field of view adjustments are applied to a user interface presented on the image display based on detected head or eye movement by a user;

FIG. 1B is a top cross-sectional view of a temple of the eyewear device of FIG. 1A depicting a visible light camera, a head movement tracker for tracking the head movement of the user of the eyewear device, and a circuit board;

FIG. 2A is a rear view of an example hardware configuration of an eyewear device, which includes an eye scanner on a frame, for use in a system for identifying a user of the eyewear device;

FIG. 2B is a rear view of an example hardware configuration of another eyewear device, which includes an eye scanner on a temple, for use in a system for identifying a user of the eyewear device;

FIGS. 2C and 2D are rear views of example hardware configurations of the eyewear device, including two different types of image displays:

FIG. 3 shows a rear perspective view of the eyewear device of FIG. 2A depicting an infrared emitter, an infrared camera, a frame front, a frame back, and a circuit board;

FIG. 4 is a cross-sectional view taken through the infrared emitter and the frame of the eyewear device of FIG. 3 ;

FIG. 5 illustrates detecting eye gaze direction;

FIG. 6 illustrates detecting eye position;

FIG. 7 depicts an example of visible light captured by the left visible light camera as a left raw image and visible light captured by the right visible light camera as a right raw image;

FIG. 8A is a side view of a projector configured to generate a visual image;

FIG. 8B is a side sectional view of a housing that encompasses the components of the system described with reference to FIG. 8A;

FIG. 8C illustrates the portion of the system that is an illumination section of projector, and the portion of projector that is a projection lens;

FIG. 8D illustrates graphs of system dimensions as a function of the curvature of the field lens;

FIG. 8E illustrates a method of generating a decentered light beam that passes through the field lens, and displacing a display to generate a display image with an angular boresight offset;

FIG. 9 illustrates a block diagram of electronic components of the eyewear device including the projector;

FIG. 10 illustrates a schematic of a portion of the controller selectively controlling the intensity of the LEDs across a large range of brightness;

FIG. 11 illustrates a table showing the forward current provided to the selected light source as a function of the selected feedback resistance value; and

FIG. 12 illustrates a method of operating the brightness control of the image.

DETAILED DESCRIPTION

This disclosure is directed to eyewear including a projector having a variable feedback loop controlling a forward current delivered to a colored light source. The colored light source is configured to generate a colored light beam to generate a displayed image. The variable feedback loop in one example has a variable resistance to selectively generate a high brightness image when the eyewear is operated outside (e.g., in a high ambient light setting), and to selectively generate a nominal brightness image when the eyewear is operated inside. A controller selectively controls the drive current delivered to the colored light source to control the brightness mode of the image.

Additional objects, advantages and novel features of the examples will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by production or operation of the examples. The objects and advantages of the present subject matter may be realized and attained by means of the methodologies, instrumentalities and combinations particularly pointed out in the appended claims.

In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. However, it should be apparent to those skilled in the art that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings.

The term “coupled” as used herein refers to any logical, optical, physical, or electrical connection, link, or the like by which signals or light produced or supplied by one system element are imparted to another coupled element. Unless described otherwise, coupled elements or devices are not necessarily directly connected to one another and may be separated by intermediate components, elements or communication media that may modify, manipulate, or carry the light or signals.

The orientations of the eyewear device, associated components and any complete devices incorporating an eye scanner and camera such as shown in any of the drawings, are given by way of example only, for illustration and discussion purposes. In operation for a particular variable optical processing application, the eyewear device may be oriented in any other direction suitable to the particular application of the eyewear device, for example up, down, sideways, or any other orientation. Also, to the extent used herein, any directional term, such as front, rear, inwards, outwards, towards, left, right, lateral, longitudinal, up, down, upper, lower, top, bottom and side, are used by way of example only, and are not limiting as to direction or orientation of any optic or component of an optic constructed as otherwise described herein.

Reference now is made in detail to the examples illustrated in the accompanying drawings and discussed below.

FIG. 1A is a side view of an example hardware configuration of an eyewear device 100, which includes a right optical assembly 180B with an image display 180D (FIG. 2A). Eyewear device 100 includes multiple visible light cameras 114A-B (FIG. 7 ) that form a stereo camera, of which the right visible light camera 114B is located on a right temple 110B.

The left and right visible light cameras 114A-B have an image sensor that is sensitive to the visible light range wavelength. Each of the visible light cameras 114A-B have a different frontward facing angle of coverage, for example, visible light camera 114B has the depicted angle of coverage 111B. The angle of coverage is an angle range which the image sensor of the visible light camera 114A-B picks up electromagnetic radiation and generates images. Examples of such visible lights camera 114A-B include a high-resolution complementary metal-oxide-semiconductor (CMOS) image sensor and a video graphic array (VGA) camera, such as 640p (e.g., 640×480 pixels for a total of 0.3 megapixels), 720p, or 1080p. Image sensor data from the visible light cameras 114A-B are captured along with geolocation data, digitized by an image processor, and stored in a memory.

To provide stereoscopic vision, visible light cameras 114A-B may be coupled to an image processor (element 912 of FIG. 9 ) for digital processing along with a timestamp in which the image of the scene is captured. Image processor 912 includes circuitry to receive signals from the visible light camera 114A-B and process those signals from the visible light cameras 114A-B into a format suitable for storage in the memory (element 934 of FIG. 9 ). The timestamp can be added by the image processor 912 or other processor, which controls operation of the visible light cameras 114A-B. Visible light cameras 114A-B allow the stereo camera to simulate human binocular vision. Stereo cameras provide the ability to reproduce three-dimensional images (element 715 of FIG. 7 ) based on two captured images (elements 758A-B of FIG. 7 ) with an overlapping field of view 713 (FIG. 7 ) from the visible light cameras 114A-B, respectively, having the same timestamp. Such three-dimensional images 715 allow for an immersive life-like experience, e.g., for virtual reality or video gaming. For stereoscopic vision, the pair of images 758A-B are generated at a given moment in time—one image for each of the left and right visible light cameras 114A-B. When the pair of generated images 758A-B from the frontward facing field of view (FOV) 111A-B of the left and right visible light cameras 114A-B are stitched together (e.g., by the image processor 912), depth perception is provided by the optical assembly 180A-B.

In an example, a user interface field of view adjustment system includes the eyewear device 100. The eyewear device 100 includes a frame 105, a right temple 110B extending from a right lateral side 170B of the frame 105, and a see-through image display 180D (FIGS. 2A-B) comprising optical assembly 180B to present a graphical user interface to a user. The eyewear device 100 includes the left visible light camera 114A connected to the frame 105 or the left temple 110A to capture a first image of the scene. Eyewear device 100 further includes the right visible light camera 114B connected to the frame 105 or the right temple 110B to capture (e.g., simultaneously with the left visible light camera 114A) a second image of the scene which partially overlaps the first image. Although not shown in FIGS. 1A-B, the user interface field of view adjustment system further includes the processor 932 coupled to the eyewear device 100 and connected to the visible light cameras 114A-B, the memory 934 accessible to the processor 932, and programming in the memory 934, for example in the eyewear device 100 itself or another part of the user interface field of view adjustment system.

Although not shown in FIG. 1A, the eyewear device 100 also includes a head movement tracker (element 109 of FIG. 1B) or an eye movement tracker (element 213 of FIG. 2B). Eyewear device 100 further includes the see-through image displays 180C-D of optical assembly 180A-B, respectfully, for presenting a sequence of displayed images, and an image display driver (element 942 of FIG. 9 ) coupled to the see-through image displays 180C-D of optical assembly 180A-B to control the image displays 180C-D of optical assembly 180A-B to present the sequence of displayed images 715, which are described in further detail below. Eyewear device 100 further includes the memory 934 and the processor 932 having access to the image display driver 942 and the memory 934. Eyewear device 100 further includes programming (element 934 of FIG. 9 ) in the memory. Execution of the programming by the processor 932 configures the eyewear device 100 to perform functions, including functions to present, via the see-through image displays 180C-D, an initial displayed image of the sequence of displayed images, the initial displayed image having an initial field of view corresponding to an initial head direction or an initial eye gaze direction (element 230 of FIG. 5 ).

Execution of the programming by the processor 932 further configures the eyewear device 100 to detect movement of a user of the eyewear device by: (i) tracking, via the head movement tracker (element 109 of FIG. 1B), a head movement of a head of the user, or (ii) tracking, via an eye movement tracker (element 113, 213 of FIGS. 2A-B, FIG. 5 ), an eye movement of an eye of the user of the eyewear device 100. Execution of the programming by the processor 932 further configures the eyewear device 100 to determine a field of view adjustment to the initial field of view of the initial displayed image based on the detected movement of the user. The field of view adjustment includes a successive field of view corresponding to a successive head direction or a successive eye direction. Execution of the programming by the processor 932 further configures the eyewear device 100 to generate a successive displayed image of the sequence of displayed images based on the field of view adjustment. Execution of the programming by the processor 932 further configures the eyewear device 100 to present, via the see-through image displays 180C-D of the optical assembly 180A-B, the successive displayed images.

FIG. 1B is a top cross-sectional view of the temple of the eyewear device 100 of FIG. 1A depicting the right visible light camera 114B, a head movement tracker 109, and a circuit board. Construction and placement of the left visible light camera 114A is substantially similar to the right visible light camera 114B, except the connections and coupling are on the left lateral side 170A. As shown, the eyewear device 100 includes the right visible light camera 114B and a circuit board, which may be a flexible printed circuit board (PCB) 140. The right hinge 126B connects the right temple 110B to a right temple 125B of the eyewear device 100. In some examples, components of the right visible light camera 114B, the flexible PCB 140, or other electrical connectors or contacts may be located on the right temple 125B or the right hinge 126B.

As shown, eyewear device 100 has a head movement tracker 109, which includes, for example, an inertial measurement unit (IMU). An inertial measurement unit is an electronic device that measures and reports a body's specific force, angular rate, and sometimes the magnetic field surrounding the body, using a combination of accelerometers and gyroscopes, sometimes also magnetometers. The inertial measurement unit works by detecting linear acceleration using one or more accelerometers and rotational rate using one or more gyroscopes. Typical configurations of inertial measurement units contain one accelerometer, gyro, and magnetometer per axis for each of the three axes: horizontal axis for left-right movement (X), vertical axis (Y) for top-bottom movement, and depth or distance axis for up-down movement (Z). The accelerometer detects the gravity vector. The magnetometer defines the rotation in the magnetic field (e.g., facing south, north, etc.) like a compass which generates a heading reference. The three accelerometers detect acceleration along the horizontal, vertical, and depth axis defined above, which can be defined relative to the ground, the eyewear device 100, or the user wearing the eyewear device 100.

Eyewear device 100 detects movement of the user of the eyewear device 100 by tracking, via the head movement tracker 109, the head movement of the head of the user. The head movement includes a variation of head direction on a horizontal axis, a vertical axis, or a combination thereof from the initial head direction during presentation of the initial displayed image on the image display. In one example, tracking, via the head movement tracker 109, the head movement of the head of the user includes measuring, via the inertial measurement unit 109, the initial head direction on the horizontal axis (e.g., X axis), the vertical axis (e.g., Y axis), or the combination thereof (e.g., transverse, or diagonal movement). Tracking, via the head movement tracker 109, the head movement of the head of the user further includes measuring, via the inertial measurement unit 109, a successive head direction on the horizontal axis, the vertical axis, or the combination thereof during presentation of the initial displayed image.

Tracking, via the head movement tracker 109, the head movement of the head of the user further includes determining the variation of head direction based on both the initial head direction and the successive head direction. Detecting movement of the user of the eyewear device 100 further includes in response to tracking, via the head movement tracker 109, the head movement of the head of the user, determining that the variation of head direction exceeds a deviation angle threshold on the horizontal axis, the vertical axis, or the combination thereof. The deviation angle threshold is between about 3° to 10°. As used herein, the term “about” when referring to an angle means±10% from the stated amount.

Variation along the horizontal axis slides three-dimensional objects, such as characters, Bitmojis, application icons, etc. in and out of the field of view by, for example, hiding, unhiding, or otherwise adjusting visibility of the three-dimensional object. Variation along the vertical axis, for example, when the user looks upwards, in one example, displays weather information, time of day, date, calendar appointments, etc. In another example, when the user looks downwards on the vertical axis, the eyewear device 100 may power down.

The right temple 110B includes temple body 211 and a temple cap, with the temple cap omitted in the cross-section of FIG. 1B. Disposed inside the right temple 110B are various interconnected circuit boards, such as PCBs or flexible PCBs, that include controller circuits for right visible light camera 114B, microphone(s) 130, speaker(s) 132, low-power wireless circuitry (e.g., for wireless short-range network communication via Bluetooth™), high-speed wireless circuitry (e.g., for wireless local area network communication via WiFi).

The right visible light camera 114B is coupled to or disposed on the flexible PCB 340 (FIG. 3 ) and covered by a visible light camera cover lens, which is aimed through opening(s) formed in the right temple 110B. In some examples, the frame 105 connected to the right temple 110B includes the opening(s) for the visible light camera cover lens. The frame 105 includes a front-facing side configured to face outwards away from the eye of the user. The opening for the visible light camera cover lens is formed on and through the front-facing side. In the example, the right visible light camera 114B has an outward facing angle of coverage 111B with a line of sight or perspective of the right eye of the user of the eyewear device 100. The visible light camera cover lens can also be adhered to an outward facing surface of the right temple 110B in which an opening is formed with an outwards facing angle of coverage, but in a different outwards direction. The coupling can also be indirect via intervening components.

Left (first) visible light camera 114A is connected to the left see-through image display 180C of left optical assembly 180A to generate a first background scene of a first successive displayed image. The right (second) visible light camera 114B is connected to the right see-through image display 180D of right optical assembly 180B to generate a second background scene of a second successive displayed image. The first background scene and the second background scene partially overlap to present a three-dimensional observable area of the successive displayed image.

Flexible PCB 140 is disposed inside the right temple 110B and is coupled to one or more other components housed in the right temple 110B. Although shown as being formed on the circuit boards of the right temple 110B, the right visible light camera 114B can be formed on the circuit boards of the left temple 110A, the temples 125A-B, or frame 105.

FIG. 2A is a rear view of an example hardware configuration of an eyewear device 100, which includes an eye scanner 113 on a frame 105, for use in a system for determining an eye position and gaze direction of a wearer/user of the eyewear device 100. As shown in FIG. 2A, the eyewear device 100 is in a form configured for wearing by a user, which are eyeglasses in the example of FIG. 2A. The eyewear device 100 can take other forms and may incorporate other types of frameworks, for example, a headgear, a headset, or a helmet.

In the eyeglasses example, eyewear device 100 includes the frame 105 which includes the left rim 107A connected to the right rim 107B via the bridge 106 adapted for a nose of the user. The left and right rims 107A-B include respective apertures 175A-B which hold the respective optical element 180A-B, such as a lens and the see-through displays 180C-D. As used herein, the term lens is meant to cover transparent or translucent pieces of glass or plastic having curved and flat surfaces that cause light to converge/diverge or that cause little or no convergence/divergence.

Although shown as having two optical elements 180A-B, the eyewear device 100 can include other arrangements, such as a single optical element depending on the application or intended user of the eyewear device 100. As further shown, eyewear device 100 includes the left temple 110A adjacent the left lateral side 170A of the frame 105 and the right temple 110B adjacent the right lateral side 170B of the frame 105. The temples 110A-B may be integrated into the frame 105 on the respective sides 170A-B (as illustrated) or implemented as separate components attached to the frame 105 on the respective sides 170A-B. Alternatively, the temples 110A-B may be integrated into temples (not shown) attached to the frame 105.

In the example of FIG. 2A, the eye scanner 113 includes an infrared emitter 115 and an infrared camera 120. Visible light cameras typically include a blue light filter to block infrared light detection, in an example, the infrared camera 120 is a visible light camera, such as a low-resolution video graphic array (VGA) camera (e.g., 640×480 pixels for a total of 0.3 megapixels), with the blue filter removed. The infrared emitter 115 and the infrared camera 120 are co-located on the frame 105, for example, both are shown as connected to the upper portion of the left rim 107A. The frame 105 or one or more of the left and right temples 110A-B include a circuit board (not shown) that includes the infrared emitter 115 and the infrared camera 120. The infrared emitter 115 and the infrared camera 120 can be connected to the circuit board by soldering, for example.

Other arrangements of the infrared emitter 115 and infrared camera 120 can be implemented, including arrangements in which the infrared emitter 115 and infrared camera 120 are both on the right rim 107B, or in different locations on the frame 105, for example, the infrared emitter 115 is on the left rim 107A and the infrared camera 120 is on the right rim 107B. In another example, the infrared emitter 115 is on the frame 105 and the infrared camera 120 is on one of the temples 110A-B, or vice versa. The infrared emitter 115 can be connected essentially anywhere on the frame 105, left temple 110A, or right temple 110B to emit a pattern of infrared light. Similarly, the infrared camera 120 can be connected essentially anywhere on the frame 105, left temple 110A, or right temple 110B to capture at least one reflection variation in the emitted pattern of infrared light.

The infrared emitter 115 and infrared camera 120 are arranged to face inwards towards an eye of the user with a partial or full field of view of the eye in order to identify the respective eye position and gaze direction. For example, the infrared emitter 115 and infrared camera 120 are positioned directly in front of the eye, in the upper part of the frame 105 or in the temples 110A-B at either ends of the frame 105.

FIG. 2B is a rear view of an example hardware configuration of another eyewear device 200. In this example configuration, the eyewear device 200 is depicted as including an eye scanner 213 on a right temple 210B. As shown, an infrared emitter 215 and an infrared camera 220 are co-located on the right temple 210B. It should be understood that the eye scanner 213 or one or more components of the eye scanner 213 can be located on the left temple 210A and other locations of the eyewear device 200, for example, the frame 105. The infrared emitter 215 and infrared camera 220 are like that of FIG. 2A, but the eye scanner 213 can be varied to be sensitive to different light wavelengths as described previously in FIG. 2A.

Similar to FIG. 2A, the eyewear device 200 includes a frame 105 which includes a left rim 107A which is connected to a right rim 107B via a bridge 106; and the left and right rims 107A-B include respective apertures which hold the respective optical elements 180A-B comprising the see-through display 180C-D.

FIGS. 2C-D are rear views of example hardware configurations of the eyewear device 100, including two different types of see-through image displays 180C-D. In one example, these see-through image displays 180C-D of optical assembly 180A-B include an integrated image display. As shown in FIG. 2C, the optical assemblies 180A-B includes a suitable display matrix 180C-D of any suitable type, such as a liquid crystal display (LCD), an organic light-emitting diode (OLED) display, a waveguide display, or any other such display.

The optical assembly 180A-B also includes an optical layer or layers 176, which can include lenses, optical coatings, prisms, mirrors, waveguides, optical strips, and other optical components in any combination. The optical layers 176A-N can include a prism having a suitable size and configuration and including a first surface for receiving light from display matrix and a second surface for emitting light to the eye of the user. The prism of the optical layers 176A-N extends over all or at least a portion of the respective apertures 175A-B formed in the left and right rims 107A-B to permit the user to see the second surface of the prism when the eye of the user is viewing through the corresponding left and right rims 107A-B. The first surface of the prism of the optical layers 176A-N faces upwardly from the frame 105 and the display matrix overlies the prism so that photons and light emitted by the display matrix impinge the first surface. The prism is sized and shaped so that the light is refracted within the prism and is directed towards the eye of the user by the second surface of the prism of the optical layers 176A-N. In this regard, the second surface of the prism of the optical layers 176A-N can be convex to direct the light towards the center of the eye. The prism can optionally be sized and shaped to magnify the image projected by the see-through image displays 180C-D, and the light travels through the prism so that the image viewed from the second surface is larger in one or more dimensions than the image emitted from the see-through image displays 180C-D.

In another example, the see-through image displays 180C-D of optical assembly 180A-B include a projection image display as shown in FIG. 2D. The optical assembly 180A-B includes a projector 150, which may be a three-color projector using a scanning mirror, a galvanometer, a laser projector, or other types of projectors. During operation, an optical source such as a projector 150 is disposed in or on one of the temples 125A-B of the eyewear device 100. Optical assembly 180A-B includes one or more optical strips 155A-N spaced apart across the width of the lens of the optical assembly 180A-B or across a depth of the lens between the front surface and the rear surface of the lens. A detailed example of a projector is shown in FIGS. 8A-8E.

As the photons projected by the projector 150 travel across the lens of the optical assembly 180A-B, the photons encounter the optical strips 155A-N. When a particular photon encounters a particular optical strip, the photon is either redirected towards the user's eye, or it passes to the next optical strip. A combination of modulation of projector 150, and modulation of optical strips, may control specific photons or beams of light. In an example, a processor controls optical strips 155A-N by initiating mechanical, acoustic, or electromagnetic signals. Although shown as having two optical assemblies 180A-B, the eyewear device 100 can include other arrangements, such as a single or three optical assemblies, or the optical assembly 180A-B may have arranged different arrangement depending on the application or intended user of the eyewear device 100.

As further shown in FIGS. 2C-D, eyewear device 100 includes a left temple 110A adjacent the left lateral side 170A of the frame 105 and a right temple 110B adjacent the right lateral side 170B of the frame 105. The temples 110A-B may be integrated into the frame 105 on the respective lateral sides 170A-B (as illustrated) or implemented as separate components attached to the frame 105 on the respective sides 170A-B. Alternatively, the temples 110A-B may be integrated into temples 125A-B attached to the frame 105.

In one example, the see-through image displays include the first see-through image display 180C and the second see-through image display 180D. Eyewear device 100 includes first and second apertures 175A-B which hold the respective first and second optical assemblies 180A-B. The first optical assembly 180A includes the first see-through image display 180C (e.g., a display matrix of FIG. 2C or optical strips and a projector (not shown)). The second optical assembly 180B includes the second see-through image display 180D (e.g., a display matrix of FIG. 2C or optical strips 155A-N and a projector 150). The successive field of view of the successive displayed image includes an angle of view between about 15° to 30, and more specifically 24°, measured horizontally, vertically, or diagonally. The successive displayed image having the successive field of view represents a combined three-dimensional observable area visible through stitching together of two displayed images presented on the first and second image displays.

As used herein, “an angle of view” describes the angular extent of the field of view associated with the displayed images presented on each of the left and right image displays 180C-D of optical assembly 180A-B. The “angle of coverage” describes the angle range that a lens of visible light cameras 114A-B or infrared camera 220 can image. Typically, the image circle produced by a lens is large enough to cover the film or sensor completely, possibly including some vignetting (i.e., a reduction of an image's brightness or saturation toward the periphery compared to the image center). If the angle of coverage of the lens does not fill the sensor, the image circle will be visible, typically with strong vignetting toward the edge, and the effective angle of view will be limited to the angle of coverage. The “field of view” is intended to describe the field of observable area which the user of the eyewear device 100 can see through his or her eyes via the displayed images presented on the left and right image displays 180C-D of the optical assembly 180A-B. Image display 180C of optical assembly 180A-B can have a field of view with an angle of coverage between 15° to 30°, for example 24°, and have a resolution of 480×480 pixels.

FIG. 3 shows a rear perspective view of the eyewear device of FIG. 2A. The eyewear device 100 includes an infrared emitter 215, infrared camera 220, a frame front 330, a frame back 335, and a circuit board 340. It can be seen in FIG. 3 that the upper portion of the left rim of the frame of the eyewear device 100 includes the frame front 330 and the frame back 335. An opening for the infrared emitter 215 is formed on the frame back 335.

As shown in the encircled cross-section 4 in the upper middle portion of the left rim of the frame, a circuit board, which is a flexible PCB 340, is sandwiched between the frame front 330 and the frame back 335. Also shown in further detail is the attachment of the left temple 110A to the left temple 325A via the left hinge 126A. In some examples, components of the eye movement tracker 213, including the infrared emitter 215, the flexible PCB 340, or other electrical connectors or contacts may be located on the left temple 325A or the left hinge 126A.

FIG. 4 is a cross-sectional view through the infrared emitter 215 and the frame corresponding to the encircled cross-section 4 of the eyewear device of FIG. 3 . Multiple layers of the eyewear device 100 are illustrated in the cross-section of FIG. 4 , as shown the frame includes the frame front 330 and the frame back 335. The flexible PCB 340 is disposed on the frame front 330 and connected to the frame back 335. The infrared emitter 215 is disposed on the flexible PCB 340 and covered by an infrared emitter cover lens 445. For example, the infrared emitter 215 is reflowed to the back of the flexible PCB 340. Reflowing attaches the infrared emitter 215 to contact pad(s) formed on the back of the flexible PCB 340 by subjecting the flexible PCB 340 to controlled heat which melts a solder paste to connect the two components. In one example, reflowing is used to surface mount the infrared emitter 215 on the flexible PCB 340 and electrically connect the two components. However, it should be understood that through-holes can be used to connect leads from the infrared emitter 215 to the flexible PCB 340 via interconnects, for example.

The frame back 335 includes an infrared emitter opening 450 for the infrared emitter cover lens 445. The infrared emitter opening 450 is formed on a rear-facing side of the frame back 335 that is configured to face inwards towards the eye of the user. In the example, the flexible PCB 340 can be connected to the frame front 330 via the flexible PCB adhesive 460. The infrared emitter cover lens 445 can be connected to the frame back 335 via infrared emitter cover lens adhesive 455. The coupling can also be indirect via intervening components.

In an example, the processor 932 utilizes eye tracker 213 to determine an eye gaze direction 230 of a wearer's eye 234 as shown in FIG. 5 , and an eye position 236 of the wearer's eye 234 within an eyebox as shown in FIG. 6 . The eye tracker 213 is a scanner which uses infrared light illumination (e.g., near-infrared, short-wavelength infrared, mid-wavelength infrared, long-wavelength infrared, or far infrared) to captured image of reflection variations of infrared light from the eye 234 to determine the gaze direction 230 of a pupil 232 of the eye 234, and also the eye position 236 with respect to the see-through display 180D.

FIG. 7 depicts an example of capturing visible light with cameras 114A-B. Visible light is captured by the left visible light camera 114A with a round field of view (FOV). 111A. A chosen rectangular left raw image 758A is used for image processing by image processor 912 (FIG. 9 ). Visible light is captured by the right visible light camera 114B with a round FOV 111B. A rectangular right raw image 758B chosen by the image processor 912 is used for image processing by processor 912. Based on processing of the left raw image 758A and the right raw image 758B, a three-dimensional image 715 of a three-dimensional scene, referred to hereafter as an immersive image, is generated by processor 912 and displayed by displays 180C and 180D and which is viewable by the user.

FIG. 8A is a side view of a projector 150 configured to generate an image, such as shown and described as projector 150 in FIG. 2D. Projector 150 includes a display 812 configured to modulate light beams impinging thereon from one or more colored light sources to generate the image, shown as a red/blue light-emitting diode (LED) light 814 and a green LED light 816. The red/blue LED light 814 selectively emits a red and blue light beam 832 that passes through respective condenser lenses 818, reflects off a dichroic lens 820, through a fly's eye 822, through a powered prism 824 and a reverse total internal reflection (RTIR) light prism 826 separated from each other by a plano spacer 828, and output at a bottom output 830 of RTIR light prism 826 to display 812 as shown. The green light 816 selectively emits a green light beam 832 through respective condenser lenses 818 and passes through the dichroic lens 820, fly's eye 822, through the powered prism 824, through the plano spacer 828, and the RTIR light prism 826, and output from the bottom RTIR light prism output 830 to display 812. The colored lights 814 and 816 are time sequenced by a light controller 829 so that only one light is on at a time, and the display 812 modulates only one colored light beam 832 at a time. The modulated light from the display 812 creates an image that is directed back into RTIR light prism 826 through bottom output 830, reflects off plano spacer 828, and exits through a vertical RTIR light prism output 834 to projection lens elements 836 for display on an image plane. The human eye integrates the modulated colored light beams displayed on the image plane to perceive a color image. The display 812 may be a digital micromirror device (DMD)® display manufactured by Texas Instruments of Dallas, Tex., although other displays are possible. Only this portion of the projector 810 described herein so far is a known digital light projection (DLP)® system architecture such as manufactured by Texas Instruments of Dallas, Tex.

To increase a field of view (FOV) of this described DLP® projector from a diagonal 25-degree FOV to a diagonal 46-degree FOV, and maintain resolution and display pixel pitch, this would result in a 1.9 × scale of the display image diagonal. By maintaining the projection lens f-stop number (f/#) and maintaining telecentricity at the projection lens, this increase in display diagonal would typically translate into a direct 1.9 × scale of the diameter of the largest element in the projection lens. Additionally, due to the need to pass the colored light beams through the RTIR prism 826, the back focal length of the projection lens would also scale, resulting in an overall length increase as well.

According to this disclosure, as shown and described with reference to FIG. 8A-FIG. 8E, by incorporating a positive power field lens, the projection lens telecentricity is maintained, but the ray bundle at the last element is significantly reduced, also reducing the size needed for the back focal length and overall length of the projection lens. A field lens is a positive-powered lens that comes after an objective lens and lies near an image plane. Additional benefit is seen on the illumination side of the projector, as the size of the powered prism 824 surfaces are reduced due to the power in the field lens. In this disclosure, the selected field lens power reduces the maximum length by 17% in each dimension (x, y, z).

There is, however, a challenge that a field lens presents specifically for a DLP® display projector. A DLP® display projector requires illumination of the DMD® display 812 at a large 34-degree input angle, and a field lens centered over the DMD® display 812 poses a problem of uniform illumination on one side of the DMD® display 812. According to this disclosure, to overcome this limitation, the projection lens is designed to support a much larger image circle diameter, and further, the display 812 is laterally displaced/shifted in the image plane toward a more uniform position. This display 812 displacement results in a boresight shift (i.e., the FOV of the projector is shifted from being parallel to the optical axis of rotational symmetry). This is advantageous in an augmented reality (AR) system because this enables the projector at a non-normal angle to a waveguide, such as used in eyewear optics, allowing for a better fit in the industrial design supporting a larger pantoscopic tilt.

According to this disclosure, a curved field lens 840 is coupled adjacent to a bottom prism face 831 forming the bottom output 830 of the RTIR light prism 826. The curved field lens 840 is configured with the powered prism 824 to decenter and angle the colored light beams 832 away from the bottom prism face 831 an angle A as shown, and evenly illuminate the display 812 that is shifted to the right in the image plane. The powered prism 824 and field lens 840 angle the light beams 832 at angle A with respect to a normal of the bottom prism face 831, such that the light beams 832 are not output perpendicular to the normal of prism face 831.

A center 846 of the display 812 is shifted from a first position 844 to the right of the projection lens 836 optical axis a distance D. The decentering of the colored light beams 832 generated by field lens 840 and powered prism 824, and shifting/positioning of the display 812, results in a favorable shifted boresight image generated by display 812 as indicated at 838 that exits the projection lens elements 836. The curved field lens 840 enables use of smaller system components, wherein the greater the curvature of the curved field lens 840 the smaller projector 150, as will be discussed with reference to FIG. 8D.

Referring to FIG. 8B, there is shown a side sectional view of a housing 860 that encompasses the components of projector 150 described with reference to FIG. 8A. The housing 860 may comprise of a material that can withstand elevated temperatures, such as generated by the light beams 832, such as metal or synthetic materials.

Referring to FIG. 8C, there is illustrated the portion of projector 150 that is the illumination section 870 of projector 150, and the portion of projector 150 that is the projection lens 872. The illumination section 870 is considered to extend from the light source 816 to the vertical output 834 formed by a vertical prism face of the RTIR light prism 826 proximate the projection lens elements 836. The projection lens 872 is considered to extend from the left side of projection lens element 840 to the right end of the projection lens elements 836 and includes various optical components such as optical components 850.

Referring to FIG. 8D, there is shown graphs of system dimensions as a function of the curvature of the field lens 840.

Graph A depicts the width dimension of the prism face 831 of RTIR light prism 826 at output 830 as a function of the curvature of field lens 840. As can be seen, the greater the curvature of the field lens 840, the narrower/smaller the prism face 831 of the RTIR prism 826 and the smaller the size of system 150.

Graph B depicts the diameter of the largest of projection lens elements 836 as a function of the field lens curvature. As can be seen, the greater the curvature of the field lens 840, the smaller the diameter of the projection lens elements 836.

Graph C depicts the length of projection lens 836 as a function of the curvature of field lens 840. As can be seen, the greater the curvature of the field lens 840, the shorter the length of the projection lens 836.

Referring to FIG. 8E, there is shown a method 880 of generating a decentered light beam using the field lens, and of generating a display image.

At block 882, the light controller 829 controls the colored light sources 814 and 816 to selectively generate a red, green, and blue (RGB) colored light beam. The light sources are selectively controlled such that only one colored light beam 832 is generated at a time.

At block 884, the power prism 824 and the RTIR prism 826 route the light beams 832 therethrough. The light beams 832 are refracted provided to the prism face 831 forming the output 830.

At block 886, the powered prism 824 and the curved field lens 840 together decenter the light beams 832 from the prism face 831. The curvature of the field lens 840 angles the light beams 832 at an angle A with respect to the prism face 831 such that the angle A is not normal to the prism face 831.

At block 888, the light beams 832 are directed by the field lens 840 to the display 812 which modulates the light beams 832 to form a visual image. The center of display 812 is shifted with respect to a center of the prism face 831, and the modulated light beams 832 uniformly illuminate the display. The light image has a downward boresight as shown at 838.

The dimension of illumination section 870 is a function of the curvature of the curved field lens 840, and the dimension of the projection lens 872 is a function of the curvature of the curved field lens 840. The greater the curvature of the field lens 840, the smaller the dimensions of components forming the projector 150 and thus the smaller the dimensions of illumination section 870 and projection lens 872.

FIG. 9 depicts a high-level functional block diagram including example electronic components disposed in eyewear 100 and 200. The illustrated electronic components include the processor 932, the memory 934, and the see-through image display 180C and 180D.

Memory 934 includes instructions for execution by processor 932 to implement functionality of eyewear 100/200, including instructions for processor 932 to control in the image 715. Processor 932 receives power from battery 950 and executes the instructions stored in memory 934, or integrated with the processor 932 on-chip, to perform functionality of eyewear 100/200, and communicating with external devices via wireless connections.

A user interface adjustment system 900 includes a wearable device, which is the eyewear device 100 with an eye movement tracker 213 (e.g., shown as infrared emitter 215 and infrared camera 220 in FIG. 2B). User interface adjustments system 900 also includes a mobile device 990 and a server system 998 connected via various networks. Mobile device 990 may be a smartphone, tablet, laptop computer, access point, or any other such device capable of connecting with eyewear device 100 using both a low-power wireless connection 925 and a high-speed wireless connection 937. Mobile device 990 is connected to server system 998 and network 995. The network 995 may include any combination of wired and wireless connections.

Eyewear device 100 includes at least two visible light cameras 114A-B (one associated with the left lateral side 170A and one associated with the right lateral side 170B). Eyewear device 100 further includes two see-through image displays 180C-D of the optical assembly 180A-B (one associated with the left lateral side 170A and one associated with the right lateral side 170B). Eyewear device 100 also includes image display driver 942, image processor 912, low-power circuitry 920, and high-speed circuitry 930. The components shown in FIG. 9 for the eyewear device 100 and 200 are located on one or more circuit boards, for example a PCB or flexible PCB, in the temples. Alternatively, or additionally, the depicted components can be located in the temples, frames, hinges, or bridge of the eyewear device 100 and 200. Left and right visible light cameras 114A-B can include digital camera elements such as a complementary metal-oxide-semiconductor (CMOS) image sensor, charge coupled device, a lens, or any other respective visible or light capturing elements that may be used to capture data, including images of scenes with unknown objects.

Eye movement tracking programming implements the user interface field of view adjustment instructions, including, to cause the eyewear device 100 to track, via the eye movement tracker 213, the eye movement of the eye of the user of the eyewear device 100. Other implemented instructions (functions) cause the eyewear device 100 and 200 to determine the FOV adjustment to the initial FOV 111A-B based on the detected eye movement of the user corresponding to a successive eye direction. Further implemented instructions generate a successive displayed image of the sequence of displayed images based on the field of view adjustment. The successive displayed image is produced as visible output to the user via the user interface. This visible output appears on the see-through image displays 180C-D of optical assembly 180A-B, which is driven by image display driver 942 to present the sequence of displayed images, including the initial displayed image with the initial field of view and the successive displayed image with the successive field of view.

As shown in FIG. 9 , high-speed circuitry 930 includes high-speed processor 932, memory 934, and high-speed wireless circuitry 936. In the example, the image display driver 942 is coupled to the high-speed circuitry 930 and operated by the high-speed processor 932 in order to drive the left and right image displays 180C-D of the optical assembly 180A-B. High-speed processor 932 may be any processor capable of managing high-speed communications and operation of any general computing system needed for eyewear device 100. High-speed processor 932 includes processing resources needed for managing high-speed data transfers on high-speed wireless connection 937 to a wireless local area network (WLAN) using high-speed wireless circuitry 936. In certain examples, the high-speed processor 932 executes an operating system such as a LINUX operating system or other such operating system of the eyewear device 100 and the operating system is stored in memory 934 for execution. In addition to any other responsibilities, the high-speed processor 932 executing a software architecture for the eyewear device 100 is used to manage data transfers with high-speed wireless circuitry 936. In certain examples, high-speed wireless circuitry 936 is configured to implement Institute of Electrical and Electronic Engineers (IEEE) 802.11 communication standards, also referred to herein as Wi-Fi. In other examples, other high-speed communications standards may be implemented by high-speed wireless circuitry 936.

Low-power wireless circuitry 924 and the high-speed wireless circuitry 936 of the eyewear device 100 and 200 can include short range transceivers (Bluetooth™) and wireless wide, local, or wide area network transceivers (e.g., cellular or WiFi). Mobile device 990, including the transceivers communicating via the low-power wireless connection 925 and high-speed wireless connection 937, may be implemented using details of the architecture of the eyewear device 100, as can other elements of network 995.

Memory 934 includes any storage device capable of storing various data and applications, including, among other things, color maps, camera data generated by the left and right visible light cameras 114A-B and the image processor 912, as well as images generated for display by the image display driver 942 on the see-through image displays 180C-D of the optical assembly 180A-B. While memory 934 is shown as integrated with high-speed circuitry 930, in other examples, memory 934 may be an independent standalone element of the eyewear device 100. In certain such examples, electrical routing lines may provide a connection through a chip that includes the high-speed processor 932 from the image processor 912 or low-power processor 922 to the memory 934. In other examples, the high-speed processor 932 may manage addressing of memory 934 such that the low-power processor 922 will boot the high-speed processor 932 any time that a read or write operation involving memory 934 is needed.

Server system 998 may be one or more computing devices as part of a service or network computing system, for example, that include a processor, a memory, and network communication interface to communicate over the network 995 with the mobile device 990 and eyewear device 100/200. Eyewear device 100 and 200 is connected with a host computer. For example, the eyewear device 100 is paired with the mobile device 990 via the high-speed wireless connection 937 or connected to the server system 998 via the network 995.

Output components of the eyewear device 100 include visual components, such as the left and right image displays 180C-D of optical assembly 180A-B as described in FIGS. 2C-D (e.g., a display such as a liquid crystal display (LCD), a plasma display panel (PDP), a light emitting diode (LED) display, a projector, or a waveguide). The image displays 180C-D of the optical assembly 180A-B are driven by the image display driver 942. The output components of the eyewear device 100 further include acoustic components (e.g., speakers), haptic components (e.g., a vibratory motor), other signal generators, and so forth. The input components of the eyewear device 100 and 200, the mobile device 990, and server system 998, may include alphanumeric input components (e.g., a keyboard, a touch screen configured to receive alphanumeric input, a photo-optical keyboard, or other alphanumeric input components), point-based input components (e.g., a mouse, a touchpad, a trackball, a joystick, a motion sensor, or other pointing instruments), tactile input components (e.g., a physical button, a touch screen that provides location and force of touches or touch gestures, or other tactile input components), audio input components (e.g., a microphone), and the like.

Eyewear device 100 may optionally include additional peripheral device elements. Such peripheral device elements may include heat sensors 940, ambient light and spectral sensors, biometric sensors, additional sensors, or display elements integrated with eyewear device 100. For example, peripheral device elements may include any I/O components including output components, motion components, position components, or any other such elements described herein. The eyewear device 100 can take other forms and may incorporate other types of frameworks, for example, a headgear, a headset, or a helmet.

For example, the biometric components of the user interface field of view adjustment 900 include components to detect expressions (e.g., hand expressions, facial expressions, vocal expressions, body gestures, or eye tracking), measure biosignals (e.g., blood pressure, heart rate, body temperature, perspiration, or brain waves), identify a person (e.g., voice identification, retinal identification, facial identification, fingerprint identification, or electroencephalogram based identification), and the like. The motion components include acceleration sensor components (e.g., accelerometer), gravitation sensor components, rotation sensor components (e.g., gyroscope), and so forth. The position components include location sensor components to generate location coordinates (e.g., a Global Positioning System (GPS) receiver component), WiFi or Bluetooth™ transceivers to generate positioning system coordinates, altitude sensor components (e.g., altimeters or barometers that detect air pressure from which altitude may be derived), orientation sensor components (e.g., magnetometers), and the like. Such positioning system coordinates can also be received over wireless connections 925 and 937 from the mobile device 990 via the low-power wireless circuitry 924 or high-speed wireless circuitry 936.

According to some examples, an “application” or “applications” are program(s) that execute functions defined in the programs. Various programming languages can be employed to create one or more of the applications, structured in a variety of manners, such as object-oriented programming languages (e.g., Objective-C, Java, or C++) or procedural programming languages (e.g., C or assembly language). In a specific example, a third party application (e.g., an application developed using the ANDROID™ or IOS™ software development kit (SDK) by an entity other than the vendor of the particular platform) may be mobile software running on a mobile operating system such as IOS™, ANDROID™ WINDOWS® Phone, or another mobile operating systems. In this example, the third-party application can invoke API calls provided by the operating system to facilitate functionality described herein.

When the eyewear 100 is used indoors, or in low ambient light settings, the brightness (luminous flux) of the displayed image 715 is sufficient for the user to view the displayed image 715. However, when the eyewear 100 is used outdoors, or in high ambient light settings, it is difficult for a user to see the displayed image 715 as the image brightness generated is sufficient for indoor use, but the image brightness is insufficient for use outdoors. Eyewear projectors 150 are very small and complex, both electrically and optically, and this disclosure provides an efficient LED brightness controller to selectively establish the brightness of the image 715. The controller generates a forward current over a large range of currents to generate a large range of image brightness. The user can select the brightness of the displayed image 715 by providing an input, such as touching a switch. An ambient light detector can also control the generated brightness of the display 715.

As shown in FIG. 10 , there is illustrated a portion of the processor 932 forming a light controller 1000 configured to control the brightness of the red/blue LEDs 814 and the green LED 816. The controller 1000 selectively generates and controls a forward current delivered to each of the LEDs 814 and 816, wherein the brightness of the beam generated by each LED is a direct function of the respective forward current. The forward current is also known as a drive current.

The controller 1000 includes a plurality of electronic switches SW4, SW5 and SW6 configured to selectively control the drive current to the respective LED. When SW4 is closed by a respective control signal generated by the processor 932, drive current is delivered from the VLED positive rail to the red LED 814. When SW5 is closed by a respective control signal generated by the processor 932, drive current is delivered to the green LED 816. When SW6 is closed by a respective control signal generated by the processor 932, drive current is delivered to the blue LED 814. The switches can be transistors, or other types of electronic switches and limitation to the type of electronic switch is not to be inferred.

The drive current delivered to each of the LEDs 814 and 816 is controlled by a closed control feedback loop including a plurality of resistors, shown as a first resistor R1 and a second resistor R2, and a drive current control device 1002. The control device 1002 is a switch, shown in this example as a power field effect transistor (FET), which is selectively controlled to be on or off by a control signal provided to an input 1004 of the FET 1002. In one example, a user can control the control signal to control the FET 1002, such as by using a control switch. In another example, the ambient light detector 1006 controls the FET 1002. When the FET 1002 is on by providing a respective control signal on control input 1004, such as by the user or the ambient light detector 1006, the resistors R1 and R2 are in parallel. When the FET 1002 is off, the resistor R2 is not part of the feedback loop, and thus only resistor R1 is in the feedback loop.

In an example as shown in FIG. 10 , resistor R1 and R2 each have the same resistance, such as 400 mOhms, such that the overall feedback loop resistance is 200 mOhms when the resistors R1 and R2 are in parallel as controlled by the FET 1002. When the FET 1002 is off, only resistor R2 is in the feedback loop and the feedback loop resistance is 400 mOhms.

As shown in FIG. 11 , when the FET 1002 is on, the drive current to the respective LED is the highest, shown in this example as 500 mA. When the FET 1002 is off, the drive current to the respective LED is the lowest, shown in this example as 247 mA. Thus, the current range is from 247 mA to 500 mA, and the brightness of each LED in a brightest mode is roughly double the brightness of each LED in a normal mode. In this example, the controller 1000 provides a high signal to the gate of the FET 1002 to turn the FET on, and provides a low signal to the FET 1002 to turn the FET off. In another example, the controller 1000 provides a low signal to the gate of FET 1002 to turn it off, and a high signal to the gate of FET 1002 to it on, and limitation to the arrangement of the control logic is not to be inferred.

FIG. 12 illustrates a method 1200 of controlling the brightness of image 715 of the projector 150.

At block 1202, the desired brightness of image 715 is selected. This can be done by a user touching a switch, such as on a temple of the eyewear, or by an ambient light detector 1006 coupled to the temple. In an example, if the eyewear 100 is being operated indoors, or in a relatively normal ambient light setting, the brightness of the image 715 is set to a nominal brightness mode. If the eyewear 100 is being operated outdoors, or in a high ambient light setting, the brightness of the image 715 is set to a high brightness mode.

At block 1204, the controller 1000 of processor 932 establishes the feedback loop of the controller 1000 for the selected display brightness mode. If the brightness of the image 715 is set to a nominal brightness, the FET 1002 is controlled by the controller 1000 to be off such that only the resistor R1 is in the feedback loop, as shown in FIG. 11 . If the brightness of the image 715 is set to the high brightness mode, the FET 1002 is controlled by the controller 1000 such that both the resistors R1 and R2 are in parallel in the feedback loop.

At block 1206, if only the resistor R1 is electrically configured in the feedback loop of controller 1000, the generated drive current delivered to the LEDs 814 and 816 is 247 mA as shown in FIG. 11 . If both resistors R1 and R2 are configured in parallel in the feedback loop, the generated drive current delivered to the LEDs 814 and 816 is 500 mA as shown in FIG. 11 .

It will be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein. Relational terms such as first and second and the like may be used solely to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “includes,” “including,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises or includes a list of elements or steps does not include only those elements or steps but may include other elements or steps not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “a” or “an” does not, without further constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

Unless otherwise stated, any and all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, including in the claims that follow, are approximate, not exact. Such amounts are intended to have a reasonable range that is consistent with the functions to which they relate and with what is customary in the art to which they pertain. For example, unless expressly stated otherwise, a parameter value or the like may vary by as much as ±10% from the stated amount.

In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various examples for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed examples require more features than are expressly recited in each claim. Rather, as the following claims reflect, the subject matter to be protected lies in less than all features of any single disclosed example. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.

While the foregoing has described what are considered to be the best mode and other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that they may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the present concepts. 

What is claimed is:
 1. A projector, comprising: a light source configured to generate a light beam; a display configured to modulate the light beam to generate an image; and a controller configured to control a brightness of the light source, wherein the controller comprises a selectively configurable feedback loop including a first resistor, a second resistor, and a switch configured to selectively establish only the first resistor in the feedback loop in a first mode, and selectively establish the first resistor and the second resistor in parallel in a second mode.
 2. The projector of claim 1, wherein the feedback loop is configurable in the first mode to generate the image having a first brightness, and the feedback loop is configurable in the second mode to generate the image having a second brightness that is greater than the first brightness.
 3. The projector of claim 2, wherein the feedback loop has a variable resistance.
 4. The projector of claim 3, wherein the feedback loop selectively controls a drive current delivered to the light source.
 5. The projector of claim 1, wherein the switch is a power field effect transistor (FET).
 6. The projector of claim 1, wherein the switch is in series with the first resistor.
 7. The projector of claim 1, wherein the controller is configured to be controlled by a user to selectively control the brightness of the display.
 8. The projector of claim 1, wherein the controller is configured to be controlled by an ambient light detector to selectively control the brightness of the display.
 9. The projector of claim 1, further comprising eyewear coupled to the display.
 10. The projector of claim 9, wherein the eyewear comprises a frame and an optical member supported by the frame.
 11. A method of using a projector, comprising: a light source configured to generate a light beam; a display configured to modulate the light beam to generate an image; and a controller having a feedback loop, the method comprising: controlling a brightness of the light source by the controller, wherein the controller selectively configures the feedback loop including a first resistor, a second resistor, and a switch to establish only the first resistor in the feedback loop in a first mode, and the switch selectively establishing the first resistor and the second resistor in parallel in a second mode.
 12. The method of claim 11, wherein the feedback loop is configured in the first mode to generate the image having a first brightness, and the feedback loop is configured in the second mode to generate the image having a second brightness that is greater than the first brightness.
 13. The method of claim 12, wherein the feedback loop has a variable resistance.
 14. The method of claim 13, wherein the feedback loop selectively controls a drive current delivered to the light source.
 15. The method of claim 11, wherein the switch is a power field effect transistor (FET).
 16. The method of claim 11, wherein the switch is in series with the first resistor.
 17. The method of claim 11, wherein the controller is configured to be controlled by a user to selectively control the brightness of the display.
 18. The method of claim 11, wherein the controller is controlled by an ambient light detector to selectively control the brightness of the display.
 19. The method of claim 11, wherein the projector further comprises eyewear coupled to the display.
 20. The method of claim 19, wherein the eyewear comprises a frame and an optical member supported by the frame. 